This invention relates to a unique series of modified or derivatized prepolymers and polymers formed from isocyanate end-capped prepolymers which are substantially comprised of ethylene oxide units. Modification is accomplished by contacting the prepolymer with a reactive compound having an NCO-reactive group and a second functional group. The NCO-reactivity can be found in sulfhydryl (--SH), amine (--NH.sub.2), alcohol (--OH) or carboxyl (--COOH) groups. The derivative compounds are characterized by additional properties associated with the second functional group inserted into the prepolymer. Hydrogels, coatings or small soluble polymeric or prepolymeric units can be formed from the modified prepolymers.
Numerous polyurethane polymers have been previously identified, among them both foamed and nonfoamed materials. Of the nonfoamed materials, quite a few hydrogel polymers, prepared from various prepolymers, have been prepared and used for widely varying applications. Typically, hydrogels are formed by polymerizing a hydrophilic monomer in an aqueous solution under conditions such that the prepolymer becomes crosslinked, forming a three-dimensional polymeric network which gels the solution. Polyurethane hydrogels are formed by polymerization of isocyanate-end capped prepolymers to create urea and urethane linkages.
Representative examples of previously disclosed polyurethane hydrogels include the following: U.S. Pat. No. 4,241,537 (Wood) discloses a plant growth media comprising a hydrophilic polyurethane gel composition prepared from chain-extended polyols; random copolymerization is preferred with up to 50% propylene oxide units so that the prepolymer will be a liquid at room temperature. U.S. Pat. No. 3,939,123 (Matthews) discloses lightly crosslinked polyurethane polymers of isocyanate terminated prepolymers comprised of poly(ethyleneoxy) glycols with up to 35% of a poly(propyleneoxy) glycol or a poly(butyleneoxy) glycol. In producing the Matthews polymer, an organic polyamine is used as a crosslinking agent. The Matthews prepolymers form a cross-linked, three dimensional structure when polymerized as taught in the patent. U.S. Pat. No. 4,182,827 (Jones) discloses a similar use of polyamines in the formation of polyurethane hydrogels.
Several types of compounds have been reacted with prepolymers or with matrix bases to act as spacing or coupling compounds in the attachment or immobilization of biologically active agents. For example, U.S. Pat. No. 4,226,935 (Fusee) discloses reacting an amino acid and/or a protein with an excess of a urethane prepolymer, curing the resulting product to form a polymer matrix, and coupling an enzyme thereto by use of a carbodiimide. U.S. Pat. No. 4,177,038 (Biebricher et al.) teaches the use of spacers which may be diamines, amino-alcohols or diols.
Modified polyurethane polymers also have been prepared. U.S. Pat. No. 4,439,585 (Gould et al.) teaches a polyurethane diacrylate composition obtained by reacting a diacrylate in the presence of a hydrophilic polyurethane resin. U.S. Pat. No. 4,485,227 (Fox) discloses a poly-(ether-urethane-urea) prepared by condensations of a prepolymer with primary diamines, then with an amine-reacting agent. U.S. Pat. No. 4,569,981 (Wenzel et al.) discloses water-dispersible plastics precursors based on isocyanate-terminated prepolymers which have been hydrophilically modified with ionic groups and/or ethylene oxide groups.
Biocompatibility is an increasingly desirable characteristic for polymeric hydrogels and hydrated polymers, which would find numerous uses in the health care field if the appropriate properties can be obtained. However, many conventional hydrogels and polymers are not taught to be biocompatible.